Manipulating Spectra
case sensitive). If one is found, the composition and density will be retrieved from the database and automatically entered into the dialog. As you define new materials, they are automatically
and transparently added to the database. Tus, it is best to carefully assign a user-friendly name and a density for each material because it facilitates reuse. In time you will build up a substantial and useful database of materials. If you modify the definition (composition or density) of an existing material, the program will ask whether you want to update the database definition.
Manipulating the Spectrum Display Te spectrum display (see the top of Figure 1) is a plotting
tool specialized for displaying x-ray spectra. It is capable of displaying up to 50 spectra simultaneously. Energy-dispersive x-ray spectra are a histogram of x-ray counts in bins of increasing energy. Te horizontal axis represents x-ray photon energy measured in electron volts (eV) and is divided into equal-sized bins. On most spectrometers these bins are nominally either 10 eV/bin wide (most common) or 5 eV/bin wide. Te vertical axis represents the count of x-ray events falling within an energy bin. If you examine a reduced range of energies, then you will notice that the spectrum is not a continuous curve but is represented by a series of steps. Spectrum display toolbar. To the leſt of the spectrum
display is the spectrum display tool bar with buttons to manipulate the vertical and horizontal scales. Te top button ( ) autoscales the axes to display all spectral data above 0 eV. Te vertical scale is set to display the highest peak (excluding the zero strobe peak). Te vertical arrow buttons modify the vertical scale. Te double arrows step by a factor of 5 and the single arrows by a factor of 2. In addition to the graphical buttons, a mouse equipped with a wheel can be used to scroll the vertical axis. When the cursor is located over the spectrum display panel, rolling the mouse wheel will increase or decrease the vertical axis. Horizontal scale changes. Te horizontal axis can be
modified using the buttons labeled “5,” “10,” “15,” or “20.” Tese buttons set the horizontal axis range to 0 eV to 5 keV, 0 eV to 10 keV, 0 eV to 15 keV, or 0 eV to 20 keV, respectively. It is possible to zoom in to different energy ranges using the energy region cursor and the doubly-opposed horizontal arrows ( ) button. Energy regions can be specified by leſt-clicking and dragging the mouse cursor within the spectrum plot panel. Te selected regions will display in blue while the drag is in process and in yellow when the leſt mouse button is released. You may select multiple regions by repeating the drag-and-click process. Be careful not to double-click in the plot panel because this engages the single channel cursor (a vertical blue line). If you do engage the single channel cursor, a second double-click will disengage it. Once one or more ranges of channels have been selected, the horizontal arrow button ( ) will zoom in to a range of energies, which minimally encompasses all selected energy ranges. It is also possible to perform many of the same actions using the spectrum display panel’s context-sensitive menu. A
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Figure 4: The energy region menu. This menu is accessed via a right mouse click over a yellow highlighted region of spectrum. It contains actions to be performed on the highlighted range of channels. Highlighted regions are created by clicking and dragging over a range of energies.
Figure 5: The main spectrum display menu. This menu contains actions to export and configure the spectrum display. The “copy → as bitmap” menu action places a low-fidelity bitmap of the spectrum display on the system clipboard. The “save → as displayed” action exports a high-fidelity representation of the spectrum display to a file.
right mouse click over the spectrum display panel will display one of two different menus. If the right click is over a highlighted (yellow) region, then a menu with actions related to the energy region will display (see Figure 4). If the right click is not over a highlighted region, then a menu with generic spectrum manipulation options will display (see Figure 5). Many of the same zoom options are available from this menu. In addition, one menu item allows you to explicitly specify ranges of channels using a dialog box to enter the energies as text values.
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